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Evidence hierarchies, one element used to determine best evidence, have been a tool of evidence-based healthcare for over 40 years (Burns et al., 2011). International groups, such as the Cochrane Library, World Health Organization (WHO), JBI, and the Agency for Healthcare Research and Quality (AHRQ) develop and apply evidence hierarchies to generate evidence-based recommendations (AHRQ, 2020; Higgins & Green, 2011; Pearson, 2005; WHO, 2012). Although there are dozens of classification systems, the overall goal is the same—to provide guidance on identifying the best evidence to change or improve practice.
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Finding and evaluating evidence, the cornerstone of evidence-based healthcare, is the second phase in the JHEBP PET process. Evidence hierarchies are a tool to rank evidence according to the rigor of the methods of the evidence under review. This system puts evidence into tiered levels and allows for a shared understanding of how to evaluate and compare each piece of literature. Once the team determines the level of evidence, they assess the quality of the evidence appropriate for the specific method used. While the type of evidence governs the level, quality speaks to the execution and reporting of the review. This combination of level and quality yields an overall determination of the strength of the evidence, which is essential to generate sound recommendations and eventual translation to practice. The Johns Hopkins Evidence-Based Practice Model and Guidelines use a five-level evidence hierarchy. This is unique in that it includes not only research evidence (Levels I, II, and III), but nonresearch evidence as well (Levels IV, V). Figure E.1 displays the JHEBP evidence hierarchy.
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Determining the level of evidence allows the team to complete the quality assessment using a corresponding quality scale. Rating scales assist in the critical appraisal of evidence by presenting a structured way to differentiate evidence of varying levels and quality. The Johns Hopkins model uses a three-point rating scale to give a grade of A (“high” quality), B (“good” quality), or C (“low” quality). Evidence with a rating of C is not included in the evidence summary and synthesis because the quality level is inadequate to generate reliable recommendations.
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Within the JHEBP Model, determining the correct level of evidence is paramount, as it will direct you to the appropriate quality appraisal tool for Research Evidence (Appendix E) or Nonresearch Evidence (Appendix F). These lead the team through a series of “yes” or “no” questions to aid in critically evaluating an article. The Hierarchy of Evidence Guide (Appendix D) provides an overview of types of literature and specifies where they fall in the schema. Differentiating between types of evidence is a learned skill and improves with direct practice. EBP teams should use caution in taking evidence at face ...